How-to Guide
How to Connect a DSP Using the Digital Audio Output
Quick answer
You've got two digital outputs. The optical SPDIF socket is on the rear panel of the unit, and a coaxial SPDIF output sits on C6 of Harness C on a brown wire. Use whichever one your processor has an input for. You don't need either one for a standard install.
What this gives you
Your signal reaches the processor without ever becoming analogue. You then tune on the numbers, not on top of whatever the RCA run picked up on the way. If you've got a long cable run down the transmission tunnel to a rear mounted processor, that run is where noise gets in.
Before you start
- A processor with an optical or a coaxial SPDIF input. Check which one before you buy a lead.
- For optical, a Toslink lead routed without a tight bend. Optical fibre doesn't like being kinked behind a dash.
- For coaxial, Harness C, which is supplied, and a 75 ohm coaxial lead to your processor.
- Your processor already powered and earthed, because the head unit only sends signal.
Step by step
- Decide which output your processor can take
Optical and coaxial carry the same signal. Only the socket differs, so your processor decides this, not the head unit.
- For optical, use the rear panel socket
You'll find the SPDIF digital audio output among the nine connections on the rear panel of the unit, alongside the HDMI output and the antenna connections. Plug the Toslink lead in before the unit goes back into the dash, because you can't reach it afterwards.
- For coaxial, use C6 on Harness C
C6 is the coaxial digital output and the wire is brown. You're on a different output to the optical one on the rear panel, not the same signal split two ways.
- Route the lead where it won't get crushed
You've got very little room behind the fascia once the unit goes back in. Run the lead first, check the unit still seats flush at all four corners, then tidy it.
- Set the processor input to digital
If you leave the processor on its analogue input, it finds nothing on the digital one. That's the step that makes a working install look like a dead output.
- Decide whether you still need the pre-outs
If you're running everything through the processor, the analogue pre-outs on Harness A and Harness C are spare. If part of your system is still on analogue, they stay, and they run at 4 volts RMS. Set any amplifier gain against that figure rather than against a 2 volt source.
If it does not work
- If you're getting nothing at the processor, check it's switched to its digital input before you touch anything at the head unit end.
- If the optical shows no light, look at the end of the Toslink lead. You'll see it glow faintly red when it's live, so no light means the lead, the socket or a kink in the run.
- If audio drops in and out on coaxial, check you're using a proper 75 ohm coaxial lead rather than a standard RCA audio lead. They're not the same thing.
- If you've got sound but no control, the processor is passing the signal through untuned. That's a processor setting, not a wiring fault.
Worth knowing
C6 sits next to the 5.1 centre channel output on C2 and the rear pre-outs on C3 and C4, so you can feed your processor digitally and an amplifier on analogue off the same harness at the same time.
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